As the wireless network develops and evolves, it carriers more and more service, and thus additional spectrum resources are required to support massive data transmission. The spectrum resources can be denoted for example by parameters such as time, frequency, bandwidth, allowable maximum emitting power and so on. The limited spectrum resources have been assigned to certain operators or services, while new available spectrum is quite rare or cost expensive. In such a situation, a concept of dynamical spectrum utilization is proposed. That is, the spectrum resources which have been assigned to certain systems or services but have not been utilized sufficiently are to be dynamically utilized. These spectrum resources belong to an unlicensed frequency band for the systems which make use of them dynamically. Before using an unlicensed frequency band, a wireless communication system should first determine whether this frequency band is available. Since the communication systems of different operators and the communication systems under different communication protocols have the fair right to use the unlicensed frequency band, how to use the same unlicensed frequency band fairly and effectively has become an urgent problem to be solved by the industry.